A central air conditioning system is required to be easily installed not only for new buildings but also for existing buildings. When installing the central air conditioning system, it is necessary to wire a power line and a signal line through a wall to multiple units such as an air conditioner, a controller, dampers and sensors of respective parts. Such wiring may be troublesome and costly.
In order to reduce such troubles and expenses, the power line and the signal line may be omitted. For example, the temperature sensor may intermittently transmit a wireless signal of detected temperature information by using a battery as a power supply. In this case, the shorter the interval of transmitting the temperature information, the higher an accuracy of temperature control in air conditioning, but on the other hand, the power consumption increases. Then, the size of the battery may need to be increased. As a result, the size of the sensor unit may be increased, and the cost of the battery may be increased.